Fans have been asking who will be singing in the episode, because Fox put out a press release hinting that only the "current" New Directions would be singing. However, a highly placed source tells us:

"Most of the songs will be sung by the Originals, with special guest stars as well. The Old New Directions."

Fox previously announced Gleeks Choice, an online initiative that calls for fans to vote for the songs to be "remixed" for the show's 100th episode, airing March 18. Fans can vote for up to 10 songs at a time and can submit votes as many times as they like.

The choice of songs includes memorable Glee moments like Rachel and Kurt's "Defying Gravity," Santana's "Valerie," and Artie's "Safety Dance." Also included is the pilot's iconic rendition of Journey's "Don't Stop Believin'," which remains somewhat of a show anthem. Previews of each song are included with each choice.